Method of manufacturing printed circuit board for semiconductor package

ABSTRACT

Disclosed is a method of manufacturing a printed circuit board for a semiconductor package, which minimizes or completely obviates masking work upon the plating of each pad for the surface treatment of a printed circuit board for a semiconductor package, thereby simplifying the overall process and increasing the mounting reliability.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2007-0037892, filed Apr. 18, 2007, entitled “Method for manufacturing printed circuit board for semi-conductor package”, which is hereby incorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to a method of manufacturing a printed circuit board (PCB) for a semiconductor package. More particularly, the present invention relates to a method of manufacturing a PCB for a semiconductor package, which minimizes masking work upon the plating of each pad for the surface treatment of a PCB for a semiconductor package.

2. Description of the Related Art

Generally, semiconductor packaging is a technique having a great influence on the proliferation of electronic hardware systems composed of active devices (e.g., semiconductor chips) and passive devices (e.g., resistors, condensers, etc.), and the packaging technique is responsible for power supply, signal connection, heat emission, and protection from the outside.

Because the packaging technique is developed to satisfy various purposes, including power supply, signal connection, and heat emission, while the package is operated in a state of being exposed to the surrounding environment, the price of products is increased, undesirably making it difficult to realize the commercialization thereof.

The international demand for semiconductor packages is increasing according to the advancement of electronic products, and in particular, the popularity of packages, such as CSP, used for notebook PCs, mobile phones, mobile data facsimile devices, disk drivers, etc., is growing.

In the PCB for a semiconductor package, when a single substrate is provided with a wire bonding pad and a pad for mounting an SMD (Surface Mount Device), such as BGA, soft gold electroplating for wire bonding is applied to the wire bonding pad, and furthermore, in the case of the BGA mounting pad, electroless OSP or electroless plating (ENIG: Electroless Nickel Immersion Gold) is applied if it is difficult to withdraw a lead wire for electroplating.

Depending on the increase in the density of the substrate for a semiconductor package, in the case where two or more purposes, including wire bonding and SMD mounting, for example, wire bonding and surface mounting techniques (when it is impossible to withdraw a lead wire for soft gold electroplating), or a surface mounting technique and a ZIF connector specification, are required, surface treatment is performed through different types of plating, including electroplating and electroless plating.

In order to conduct the above-mentioned different types of plating, masking work using a dry film or peelable ink is carried out. In this case, however, many problems related to the masking work are caused, including design limitations upon the masking of a plating resist.

Below, with reference to FIGS. 3A to 3G, the method of manufacturing a PCB for a semiconductor package according to a conventional technique is described.

According to a widely known method in the art, a PCB 400, including a resin substrate 401, and wire bonding pads 402, 405 and SMD mounting pads 403, 404 formed thereon and having a predetermined circuit pattern, is prepared, and a solder resist layer 406 is formed on the portion of the PCB 400 other than the wire bonding pads 402, 405 and the SMD mounting pads 403, 404 (FIG. 3A).

Subsequently, a first plating resist 407, such as a dry film, is applied on the portion of the PCB other than the SMD mounting pads 403, 404, to thus mask it (FIG. 3B), after which electroless plating and electroplating are typically conducted, thus forming electroless nickel/gold (ENIG) layers 408, 409 on the SMD mounting pads 403, 404 (FIG. 3C). As in the ENIG layer 408, an example of which is shown in FIG. 3C, the ENIG layer is provided in the form of a double layer including an electroless nickel plating layer 408 a and an electroless gold plating layer 408 b.

The first plating resist 407 is removed (FIG. 3D), and a second plating resist 410 is applied on the portion of the PCB other than the wire bonding pads 402, 405, to thus mask it (FIG. 3E). Through typical soft gold electroplating, nickel/gold electroplating layers 411, 412 are formed on the wire bonding pads 402, 405 (FIG. 3F). As such, as in the nickel/gold electroplating layer 412 illustrated in this drawing, the nickel/gold electroplating layer is composed of a double layer including a nickel electroplating layer 412 a and a gold electroplating layer 412 b. Finally, the second plating resist 410 is removed, thus completing surface treatment (FIG. 3G).

With reference to FIGS. 4A to 4J, the method of manufacturing a PCB for a semiconductor package according to another conventional technique is described.

According to a widely known method in the art, a PCB 500, including wire bonding pads 503, 506, SMD mounting pads 504, 505, and ZIF connector pads 507 and having a predetermined circuit pattern, is prepared. The wire bonding pads 503, 506 and the SMD mounting pads 504, 505 are formed on a rigid resin substrate 501, and the ZIF connector pads 507 are formed below the resin substrate 501 with a polyimide coverlay 502 disposed therebetween, in which a coverlay adhesive 508 is loaded into spaces between the ZIF connector pads 507. A solder resist layer 509 is formed on the portion of the PCB 500 other than the wire bonding pads 503, 506, the SMD mounting pads 504, 505, and the ZIF connector pads 507 (FIG. 4A).

Subsequently, a first plating resist 510 is applied on the portion of the PCB other than the SMD mounting pads 504, 505, to thus mask it (FIG. 4B), after which electroless plating and electroplating are typically conducted, thus forming ENIG layers 511, 512 on the SMD mounting pads 504, 505 (FIG. 4C). As in the ENIG layer 511, an example of which is shown in FIG. 4C, the ENIG layer is provided in the form of a double layer including an electroless nickel plating layer 511 a and an electroless gold plating layer 511 b.

The first plating resist 510 is removed (FIG. 4D), and a second plating resist 513 is applied on the portion of the PCB other than the wire bonding pads 503, 506, to thus mask it (FIG. 4E), after which typical soft gold electroplating is conducted, thus forming nickel/gold electroplating layers 514, 515 on the wire bonding pads 503, 506 (FIG. 4F). As such, as in the nickel/gold electroplating layer 515, illustrated in this drawing, the nickel/gold electroplating layer is composed of a double layer including a nickel electroplating layer 515 a and a gold electroplating layer 515 b.

The second plating resist 513 is removed (FIG. 4G), and a third plating resist 516 is applied on the portion of the PCB other than the ZIF connector pad 507, to thus mask it (FIG. 4H), after which typical direct gold electroplating is carried out, thus forming a gold electroplating layer 517 on the ZIF connector pad 507 (FIG. 4I). The third plating resist 516 is removed, thereby completing surface treatment (FIG. 4J).

As mentioned above, the method of manufacturing the PCB for a semiconductor package according to the conventional techniques suffers because the masking work should be conducted at least two or three times when conducting two or three types of plating, undesirably making it easy for gold plating to be poor in places due to the penetration of the masking solution, and generating defects due to the residual plating resist.

Further, in the case where the plating layer is formed on the wire bonding pad through electroless soft gold plating, lead wire problems may be solved, but the wire bonding properties may be relatively deteriorated. Moreover, the electroless soft gold plating typically results in poor SMD mounting reliability, and is also problematic in that the running cost is at least doubled.

SUMMARY OF THE INVENTION

Leading to the present invention, intensive and extensive research into avoiding the problems encountered in the related art resulted in the finding that the surface treatment of a PCB for a semiconductor package may be conducted in a manner such that ENIG plating is conducted on both a wire bonding pad and an SMD mounting pad, after which gold electroplating is performed to thus form a gold electroplating layer on the wire bonding pad and/or ZIF connector pad, and only the SMD mounting pad to which a plating lead wire is connected, thereby minimizing the masking work and satisfying the properties required for respective pads.

Accordingly, an aspect of the present invention is to provide a method of manufacturing a PCB for a semiconductor package, which is capable of minimizing or completely obviating masking work in the surface treatment of the PCB for a semiconductor package.

Another aspect of the present invention is to provide a method of manufacturing a PCB for a semiconductor package, which is capable of economically and efficiently satisfying the respective properties required for the outermost pads of the PCB for a semiconductor package.

According to a preferred embodiment of the present invention, a method of manufacturing a PCB for a semiconductor package may include (a) providing a PCB for a package, including wire bonding pads and SMD mounting pads and having a predetermined circuit pattern; (b) forming a solder resist layer on the portion of the PCB, other than the wire bonding pads and the SMD mounting pads; (c) forming an ENIG layer, composed of an electroless nickel plating layer and an electroless gold plating layer, on each of the wire bonding pads and SMD mounting pads, through electroless nickel plating and electroless gold plating; and (d) forming a gold electroplating layer on the ENIG layer of the SMD mounting pad to which a plating lead wire is connected, among the SMD mounting pads, and the ENIG layer of each of the wire bonding pads, through gold electroplating.

In the above method, of the ENIG layer, the electroless gold plating layer may have a thickness ranging from 0.01 μm to 0.1 μm, and the electroless nickel plating layer may have a thickness ranging from 0.3 μm to 15 μm.

The gold electroplating layer may have a thickness ranging from 0.1 μm to 1.0 μm.

According to another embodiment of the present invention, a method of manufacturing a PCB for a semiconductor package may include (a) providing a PCB for a package, including wire bonding pads, SMD mounting pads and ZIF connector pads and having a predetermined circuit pattern; (b) forming a solder resist layer on the portion of the PCB, other than the wire bonding pads, the SMD mounting pads, and the ZIF connector pad; (c) applying a plating resist on the portion of the PCB, other than the wire bonding pads and the SMD mounting pads; (d) forming an ENIG layer, composed of an electroless nickel plating layer and an electroless gold plating layer, on each of the wire bonding pads and SMD mounting pads, through electroless nickel plating and electroless gold plating; (d) removing the plating resist; and (e) forming a gold electroplating layer on the ENIG layer of the SMD mounting pad to which a plating lead wire is connected, among the SMD mounting pads, the ENIG layer of each of the wire bonding pads, and the ZIF connector pad, through gold electroplating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are sectional views sequentially illustrating the process of manufacturing a PCB for a semiconductor package, according to a first embodiment of the present invention;

FIGS. 2A to 2E are sectional views sequentially illustrating the process of manufacturing a PCB for a semiconductor package, according to a second embodiment of the present invention;

FIGS. 3A to 3G are sectional views sequentially illustrating the process of manufacturing a PCB for a semiconductor package, according to a conventional technique; and

FIGS. 4A to 4J are sectional views sequentially illustrating the process of manufacturing a PCB for a semiconductor package, according to another conventional technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a detailed description will be given of the present invention, with reference to the appended drawings.

In FIGS. 1A to 1C, the method of manufacturing a PCB for a semiconductor package, according to a first embodiment of the present invention, is schematically illustrated and is described below.

According to a widely known method in the art, a PCB 100, including a resin substrate 101, and wire bonding pads 102, 105 and SMD mounting pads 103, 104 formed thereon and having a predetermined circuit pattern, is prepared. In these drawings, the inner layer structure of the substrate is omitted to simplify the description, and only a single side thereof is illustratively shown, but any substrate may be used, without limitation, including double-sided, single-sided or multilayered BGA or MLB substrates. As the resin substrate 101, any substrate may be used, without limitation, including an epoxy resin substrate, a fluorinated resin substrate, etc., as long as it is known in the art. The material for the circuit pattern is not particularly limited, as long as it is conductive metal typically used in the art. Particularly useful is copper.

On the portion of the PCB 100 thus prepared, other than wire bonding pads 102, 105 and the SMD mounting pads 103, 104, a solder resist is typically applied, cured, and opened, thus forming a solder resist layer 106 (FIG. 1A). The solder resist is typically formed of photosensitive material.

Then, electroless nickel plating and electroless gold plating are performed, thus forming electroless nickel immersion gold (ENIG) layers 107, 108, 109, 110 on respective wire bonding pads 102, 105 and respective SMD mounting pads 103, 104 (FIG. 1B). As in the ENIG layer 109, enlarged for illustration in FIG. 1B, the ENIG layer is provided in the form of a double layer including an electroless nickel plating layer 109 a and an electroless gold plating layer 109 b. The thickness of the electroless gold plating layer of the ENIG layer may range from about 0.01 μm to about 0.1 μm depending on the requirements of efficacy versus economy. The thickness of the electroless nickel plating layer of the ENIG layer may range from about 0.3 μm to abut 15 μm, depending on the requirements of efficacy versus economy.

Subsequently, gold electroplating is carried out, so that gold electroplating layers 111, 113, 112 are formed respectively on the ENIG layers 107, 110 of the wire bonding pads 102, 105 and the ENIG layer 109 of the SMD mounting pad 104 to which a plating lead wire is connected (FIG. 1C). That is, both the wire bonding pads 102, 105 are connected with the plating lead wires for electroplating, and, among the SMD mounting pads, only the SMD mounting pad 104 is connected with a plating lead wire for electroplating as needed, thereby enabling gold electroplating to be conducted via such plating lead wires. Such gold electroplating may be performed through a plating process called soft gold electroplating, but nickel plating is omitted because there is no dissolution behavior of Cu. The gold electroplating layers 111, 112, 113 may have a thickness ranging from about 0.1 μm to about 1.0 μm, depending on the requirements of efficacy versus economy.

In this way, the ENIG layers 107, 110 and the gold electroplating layers 111, 113 are sequentially formed on the wire bonding pads 102, 105, and the ENIG layer 108 may be formed alone on the SMD mounting pad 103, or the ENIG layer 109 and the gold electroplating layer 112 may be formed together on only the SMD mounting pad 104 having the plating lead wire connected thereto. Thereby, the plating lead wires may be limitedly designed, and therefore the degree of freedom of CAD may be increased. Further, the masking work, which is conventionally conducted two times, is omitted, thus decreasing the process time, increasing the degree of freedom of design, and averting various causes of defects occurring when conducting the masking work. Furthermore, the use of the wire bonding pad alone advantageously enables the formation of an alignment mark.

Turning to FIGS. 2A to 2E, the method of manufacturing a PCB for a semiconductor package according to a second embodiment of the present invention is schematically illustrated, and is mentioned below.

According to a widely known method in the art, a PCB 300 including wire bonding pads 303, 306, SMD mounting pads 304, 305, and ZIF connector pads 307 and having a predetermined circuit pattern, is prepared. The wire bonding pads 303, 306, and SMD mounting pads 304, 305 are formed on a rigid resin substrate 301, and the ZIF connector pads 307 are formed below the rigid resin substrate 301 with a polyimide flexible substrate or a polyimide coverlay 302 disposed therebetween, in which a coverlay adhesive 308 is loaded into spaces between the ZIF connector pads 307, but the present invention is not limited thereto.

In these drawings, the inner layer structure of the substrate is omitted for simplicity of description, and only a single side thereof is illustrated, but any substrate may be used, without limitation, including double-sided, single-sided or multilayered BGA or MLB substrates. As the resin substrate 301, any substrate may be used, without limitation, including an epoxy resin substrate, a fluorinated resin substrate, etc., as long as it is known in the art. The material for the circuit pattern is not particularly limited as long as it is conductive metal typically used in the art. Particularly useful is copper.

On the portion of the PCB 300 thus prepared, other than the wire bonding pads 303, 306, the SMD mounting pads 304, 305, and the ZIF connector pads 307, a solder resist is typically applied, cured and opened, thus forming a solder resist layer 309 (FIG. 2A). The solder resist is typically formed of photosensitive material.

Subsequently, a plating resist 310 is applied on the portion of the PCB 300 other than the wire bonding pads 303, 306 and the SMD mounting pads 304, 305, to thus mask it (FIG. 2B). Examples of the plating resist 310 include, but are not limited to, a dry film, and peelable ink.

Subsequently, electroless nickel plating and electroless gold plating are performed, thus forming ENIG layers 311, 312, 313, 314 on the wire bonding pads 303, 306 and the SMD mounting pads 304, 305 exposed by the plating resist 310 (FIG. 2C). As in the ENIG layer 312 enlarged for illustration in FIG. 2C, the ENIG layer is provided in the form of a double layer including an electroless nickel plating layer 312 a and an electroless gold plating layer 312 b. The thickness of the electroless gold plating layer of the ENIG layer may range from about 0.01 μm to about 0.1 μm, depending on the requirements of efficacy versus economy. The thickness of the electroless nickel plating layer of the ENIG layer may range from about 0.3 μm to about 15 μm, depending on the requirements of efficacy versus economy.

Subsequently, the plating resist 310 is removed (FIG. 2D), and direct gold electroplating is performed, thus forming gold electroplating layers 315, 317, 318, 316 respectively on the ENIG layers 311, 314 of the wire bonding pads 303, 306, the ZIF connector pad 307, and the ENIG layer 313 of the SMD mounting pad 305, to which a plating lead wire is connected (FIG. 2E). That is, all the wire bonding pads 303, 306 and the ZIF connector pad 307 are connected with the plating lead wires for electroplating, and, among the SMD mounting pads, only the SMD mounting pad 305 is connected with a plating lead wire for electroplating as needed, thereby enabling the gold electroplating to be conducted via such plating lead wires. The gold electroplating may be carried out through a plating process called direct gold electroplating. The gold electroplating layers 315, 316, 317, 318 thus formed may have a thickness ranging from about 0.1 μm to about 1.0 μm, depending on the requirements of efficacy versus economy.

In this way, the masking work is conducted once, whereby the ENIG layers 311, 314 and the gold electroplating layers 315, 317 are formed on the wire bonding pads 303, 306, and the ENIG layer 312 may be formed on the SMD mounting pad 304 alone, or the ENIG layer 313 and the gold electroplating layer 316 may be formed together on only the SMD mounting pad 305 having the plating lead wire connected thereto. Further, only the gold electroplating layer 308 is formed on the ZIF connector pad 307. Thereby, the plating lead wires may be limitedly designed, thus increasing the degree of freedom of a CAD. In addition, the masking work, which is conventionally conducted three times, may be conducted once, consequently decreasing the process time, increasing the degree of freedom of design, and averting various causes of defects that occur when conducting the masking work. Furthermore, the use of the wire bonding pad alone advantageously enables the formation of an alignment mark.

The method of manufacturing the PCB for a semiconductor package according to the present invention may be applied to image sensor packages for camera modules, for example, BGA substrates, including COB (Chip On Board) and SIP (System In Package) substrates, but the present invention is not limited thereto.

Although the preferred embodiments of the present invention, with regard to the method of manufacturing the PCB for a semiconductor package, have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible within the technical spirit of the invention.

As described hereinbefore, the present invention provides a method of manufacturing a PCB for a semiconductor package. According to the method of the present invention, high defect rates, attributable to several rounds of masking work, may be minimized, and the process time may be decreased.

The masking work, which is conventionally performed two or three times in the course of surface treatment, may be completely omitted or performed once, thereby simplifying the overall process and improving the mounting reliability.

Further, the respective properties required for the outermost pads of the PCB for a semiconductor package may be economically and efficiently satisfied.

Simple modifications, additions and substitutions fall within the scope of the present invention as defined in the accompanying claims. 

1. A method of manufacturing a printed circuit board for a semiconductor package, comprising: (a) providing a printed circuit board for a package, including wire bonding pads and surface mount device mounting pads and having a predetermined circuit pattern; (b) forming a solder resist layer on a portion of the printed circuit board, other than the wire bonding pads and the surface mount device mounting pads; (c) forming an electroless nickel immersion gold layer, composed of an electroless nickel plating layer and an electroless gold plating layer, on each of the wire bonding pads and surface mount device mounting pads, through electroless nickel plating and electroless gold plating; and (d) forming a gold electroplating layer on the electroless nickel immersion gold layer of the surface mount device mounting pad to which a plating lead wire is connected, among the surface mount device mounting pads, and the electroless nickel immersion gold layer of each of the wire bonding pads, through gold electroplating.
 2. The method as set forth in claim 1, wherein the electroless gold plating layer of the electroless nickel immersion gold layer has a thickness ranging from 0.01 μm to 0.1 μm.
 3. The method as set forth in claim 1, wherein the electroless nickel plating layer of the electroless nickel immersion gold layer has a thickness ranging from 0.3 μm to 15 μm.
 4. The method as set forth in claim 1, wherein the gold electroplating layer has a thickness ranging from 0.1 μm to 1.0 μm.
 5. A method of manufacturing a printed circuit board for a semiconductor package, comprising: (a) providing a printed circuit board for a package, including wire bonding pads, surface mount device mounting pads and ZIF connector pads and having a predetermined circuit pattern; (b) forming a solder resist layer on a portion of the printed circuit board, other than the wire bonding pads, the surface mount device mounting pads, and the ZIF connector pad; (c) applying a plating resist on a portion of the printed circuit board, other than the wire bonding pads and the surface mount device mounting pads; (d) forming an electroless nickel immersion gold layer, composed of an electroless nickel plating layer and an electroless gold plating layer, on each of the wire bonding pads and surface mount device mounting pads, through electroless nickel plating and electroless gold plating; (e) removing the plating resist; and (f) forming a gold electroplating layer on the electroless nickel immersion gold layer of the surface mount device mounting pad to which a plating lead wire is connected, among the surface mount device mounting pads, the electroless nickel immersion gold layer of each of the wire bonding pads, and the ZIF connector pad, through gold electroplating.
 6. The method as set forth in claim 5, wherein the electroless gold plating layer of the electroless nickel immersion gold layer has a thickness ranging from 0.01 μm to 0.1 μm.
 7. The method as set forth in claim 5, wherein the electroless nickel plating layer of the electroless nickel immersion gold layer has a thickness ranging from 0.3 μm to 15 μm.
 8. The method as set forth in claim 5, wherein the gold electroplating layer has a thickness ranging from 0.1 μm to 1.0 μm. 